I'd love to see a program that allows you to specify which sites are opened by which browser.
Here's how I picture it. SpecifSite sits in the the tray, and when clicked opens a set of collapsible full width frames corresponding to each of the browsers you have installed on your computer. I think they should be cataloged the first time you run SpecifSite. Under each listing for each browser there's a plus sign, and a delete x. You add URLs under each browser, and they open to that browser as long as SpecifSite is running. If you've already added a URL, and want to edit it, highlight the listing, and hit the plus sign again. If the site isn't added to SpecifSite then the default browser retains control.
Options: If the programming is too difficult to list a general URL, how about the path to any shortcut you designate? If anyone has heard of a software like this I apologize, but I've never run into anything like it before, and my searches didn't find anything.
Inspiration: Browsers are getting so good I'm finding I prefer Firefox for much of my general surfing (this month's Firefox sold me into making it my default browser for the first time ever...blazing fast) but my preference for a full screen media page I visit daily is still IE9. I bet I'd find some sights I like best with Chrome too. Then there's my laziness when opening a page of stats on one of my own websites, that I wrote the password on a retired computer, but a certain browser still has it retained.